'1 



'Ti. /^^ ^y€.tL^^--. ./ /^ 



^T^e-t- 



O'ioERVATIONS 



ON THE 



GEI\US UNIO, 



TOGETHER WITH 



DESCRIPTIONS OF NEW GENERA AND SPECIES IN THE FAMILIES 



NAIADES, CONCHA, COLIMAGEA, LYMN^A^A, ME- 



LANIANA ANb P'.RISTOMIANA : 



1"*^ 



VVri'H COLOURED PLATEt^. 



BY 







ISAAC LEA, 



MEHOBR OF THE AMERICAN PHILOSOPHICAL SOCIETY, 

 ETC. ETC. 



PHILAUKLI'HI A 

 PRINTED FOR THL AUTHOR, 



BY JAMES KAV, JUN. AND CO. 



JavM 



